This invention relates to instruments for use in surgery. More particularly, this invention relates to surgical instruments with an auto-regulating heater.
It is known to provide surgical scalpels which employ a blade with an adjacent resistive heating element. The resistive heating element provides thermally-enhanced cutting, in addition to hemostasis, when electrical current is passed through the element. Although such resistive heating elements can be readily brought to a suitably high and constant temperature in air prior to contacting tissue, they rapidly cool when brought into contact with tissue. During surgery, non-predictable and continually varying portions of the blade contact the tissue as it is being cut. As the blade cools, its ability to cut tissue and provide hemostasis becomes markedly less effective. Furthermore, tissue tends to adhere to the blade. If additional power is applied by conventional means to counteract this cooling, the additional power may be delivered to the uncooled portions of the blade, thus resulting in tissue damage and blade deterioration.
Shaw U.S. Pat. No. 4,185,632 shows an improved surgical cutting instrument in which the temperature of the cutting portion of the blade is self-regulating. Radio frequency electrical currents maintain the temperature within an elevated preselected temperature range. These currents flow within variable skin depths in an electrical conductor disposed near the cutting edge of the blade. This variable skin depth effect produces self-regulation of the blade temperature.
Although the cutting instrument shown in the above-referenced Shaw U.S. Pat. No. 4,185,632 has improved temperature regulation over other surgical scalpels, further improvements are possible. For example, such instruments may be designed to provide low cost and simplicity of manufacturing.
Additionally, reducing the adherence of tissue to a surgical instrument is also desirable. Coagulum buildup and sticking limits the usefulness of an instrument and may cause undesirable tissue damage and bleeding. Also, the adherence of tissue to surgical instruments limits the surgeon's control of the instrument.
In light of the above, it would therefore be desirable to provide a low cost, easy to manufacture, surgical instrument with an auto-regulating heater for providing temperature regulation.
It would still further be desirable to provide a surgical instrument which reduces the adherence of tissue and coagulum to the instrument.